Centrifugal clutches are known in the art in which one or more clutch shoes are retained in retracted positions by springs until sufficient centrifugal force acts on the shoes to overcome the force of the retaining springs, whereupon the clutch shoes are actuated and swing outwardly to engage a stationary clutch housing or drum. These clutch constructions normally have a pair of arcuate-shaped clutch shoes which are pivotally mounted on a clutch braking plate and arranged in an end-to-end relationship with respect to each other. The braking plate is affixed to a drive shaft which is operably connected to a motor. The clutch shoes have various spring arrangements for biasing the shoes toward a retracted position, wherein the spring retaining tensions must be overcome by the centrifugal force exerted on the shoes during rotation of the driven member.
U.S. Pat. No. 4,296,852 issued to Luerken discloses an automatic two-way centrifugal clutch having a pair of clutch shoes mounted for pivotal movement on a rotating drive member. Each clutch shoe has a first state in which friction pads are in contact with a clutch drum, a second state in which the clutch shoes are out of contact with the clutch drum, and a third state in which the friction pads are in driving contact with the clutch drum. At least two spring members are connected to the clutch shoes for radially urging the friction pads against the clutch drum when the speed of rotation of the drive member is below a first predetermined speed. When the rotational speed of the rotating drive member is greater than the first speed, centrifugal forces overcome the spring force and pivot the clutch shoes to a position wherein the friction pads are out of engagement with the clutch drum. If the rotation speed is greater than a second predetermined speed, the centrifugal force urges clutch driving surfaces into driving contact with the clutch drum.
Another centrifugal clutch construction is disclosed in U.S. Pat. No. 4,226,320 to St. John. The St. John patent discloses a centrifugal clutch having a driving flange mounted on a hub which is adapted to be mounted on a driveshaft. A pair of clutch shoes are pivotally mounted at diagonally opposite ends of the shoes on the drive flange by a pair of pins which are cantilevered axially outwardly from the drive flange. The clutch shoes are mounted in end-to-end relationship with respect to each other. Extension springs bias the swinging ends of the clutch shoes toward a retracted position. The clutch shoes are adapted to move outwardly under the influence of centrifugal force and overcome the radial biasing effect of the springs to engage and drive a concentrically mounted clutch housing. A plurality of weight plates are mounted on the webs of the clutch shoes to provide various operating characteristics without changing the basic clutch construction.
As disclosed above, both centrifugal clutch constructions utilize radially operative helical clutch springs. It is known in the art that helical clutch springs and various other small working parts associated with the clutch springs often fail prior to complete failure of other clutch members. As such, the clutch springs are known to require replacement or repair. In addition, to adjust the performance of prior art clutches in opposite directions different springs having different degrees of spring bias are required that further complicate construction and servicing of such clutches.
It is therefore contemplated to provide a bi-directional centrifugal clutch which eliminates utilization of helical clutch springs or associated small parts while affording an efficient, low maintenance, bi-directional centrifugal clutch.